It sounds like you are referring to the model of the original PlayStation (PS1), which was the European/Australian variant, and its BIOS file commonly named scph5502.bin (with a v3.0 or later revision).
The file is the system firmware (BIOS) for the European (PAL) PlayStation 1 model SCPH-5502 . Specifically, this file corresponds to Version 3.0E of the BIOS, which was released in early 1997. Overview of SCPH-5502 v3.0E playstation scph5502 v30 europe bios scph5502bin
certutil -hashfile scph5502.bin MD5
This model utilized the PU-18 motherboard , which simplified the chipset with digital servos for focus and tracking, replacing the manual calibration needed in older units. SCPH-5502 It sounds like you are referring to